Falkenberg, Sweden —In Scandinavia, pre-fabricated houses are popular. One of the leading manufacturers of the steerable revolving saws used in making such homes—Randek Maskin AB—has integrated object-oriented software into its product's control system. As a result, the integrated steering facility of the company's 720PC Series cross-cutting saw takes instructions directly from the CAD system.
720PC Series saws are equipped with a graphical touch screen. The program controlling the saw uses a Frameworx-based HMI from GE Fanuc (see box, page 31). The operator can see in real time on the screen how the finished detail will look, and can easily change any variable by clicking on it. The graphical picture will update immediately and show what the detail looks like after the changes. The saw program will process all necessary parameters, such as revolving, inclination, and position of center line. The risk for miscalculations or other common problems of manual programming is almost eliminated since the operator has a full overview of each step in the sawing process.
For more advanced manufacturers, the saw features built-in CAD/CAM transfer for the most common programs on the market. The saw also has a network card and can be connected over a network through the TCP/IP protocol. With this CAD transfer, the operator downloads a project from the network directly into the saw.
Randek realized that by adopting Frameworx, it could make the necessary calculations in structured text, while controlling its machines in ladder logic. Also, the overarching machine control could be programmed in the Flowchart format, which would also be able to communicate with the different ladder functions.
There were several key advantages of the Frameworx solution:
HMI and machine control are integrated in a single program;
variables can be allocated "meaningful names" instead of strings of numeric code;
there are good opportunities for test-running the program;
processor errors can be removed when programming because there is no need for a PLC;
easy collaboration with the saw customer during development.
Randek acknowledges that operating reliability for the Soft PLC is still relatively unknown. Also there could be questions over possible interference from other programs running on the involved PCs.
Randek therefore took precautions in the set up to minimize the risks. Rolf Lundquist, spokesman for GE Fanuc in Sweden, says, "For Randek, we selected a panel-mounted industrial-PC to guarantee the robust construction and support the software. And instead of mouse and keyboard, a touchscreen was chosen."
The crosscutting saw has four axes that need to be positioned both rapidly and accurately. To achieve this, the company uses a high-speed counter card with a scantime of 1 ms. Because of the high-speed counter card, the program is not scantime-dependent.
On the stability of the PC-based system, Lundquist notes, "So far, neither the application nor Windows NT has crashed. During the development it did crash a few times but without damaging the application." For critical applications, he adds, there is software on the market such as VentureCom's 'Hard Real Time' to "guarantee" program stability. Also, some parts of Windows NT Resources make it less vulnerable to disturbance.
For more information
about Frameworx from GE Fanuc: Enter 540 The 720PC saw from Randek Maskin AB:
Frameworx is an object-oriented software technology for factory control and automation from GE Fanuc. It enables PC-based control, HMI, and system management software to operate in a single Windows NT environment. Systems integrators, OEMs, and engineers can develop control logic, HMI animations, and systems management parameters simultaneously by the simple process of dragging and dropping objects between different programs.
Furthermore, the Frameworx Navigator feature gives organizational control over projects and related files such as Word documents, Excel spreadsheets, and CAD drawings. Its Toolchest function contains 2,000 pre-configured objects, which can be dragged to the user's graphical panel and edited. Customization is also possible within the Toolchest.
Because Frameworx is an open-component system, based on Active-X, COM/DCOM, and object linking and embedding, it can also host and integrate third-party applications and software.